Morphological effect of gold nanoparticles on the adsorption of bovine serum albumin.

Various properties of gold nanoparticles (GNPs) are found to play crucial roles in their biological activity. Among them, the morphology and surface chemistry are extremely important. This is because of differences in surface energies of various crystal facets arising from a large fraction of edges, corners and vertices. In the present work, we provide a comparative study on the adsorption and binding affinities of bovine serum albumin (BSA) onto triangular gold nanoplates (TGNP) and gold nanorods (GNR). The results were compared with similar size of both CTAB and citrate stabilized spherical GNPs. Our data suggested stronger binding of BSA on citrate stabilized spherical GNPs whereas TGNP shows the weakest binding among all the GNPs. A blue shift of approximately 20 nm in tryptophan fluorescence was observed for all CTAB stabilized GNPs, indicating the local dielectric changes surrounding the tryptophan residue. Loss of the secondary structure was also observed for all CTAB stabilized GNPs. No spectral shift was observed for citrate stabilized spherical GNPs though maximum quenching of fluorescence and minimum structural loss was observed. With the help of molecular simulation recently developed by our group, a binding model is proposed to explain all the above experimental results.